There has been an increasing interest in biodiesel fuels as a supplement to, or replacement for, traditional fossil fuels. The term “biodiesel” is used for a variety of ester-based oxygenated fuels made from vegetable oils, fats, greases, or other sources of triglycerides. It is a nontoxic and biodegradable substitute and supplement for petroleum diesel. Even in blends as low as 20% biodiesel and 80% petroleum diesel (B20), biodiesel can substantially reduce the emission levels and toxicity of diesel exhaust. Biodiesel has been designated as an alternative fuel by the United States Department of Energy and the United States Department of Transportation, and is registered with the United States Environmental Protection Agency as a fuel and fuel additive. It can be used in any diesel engine, without the need for mechanical alterations, and is compatible with existing petroleum distribution infrastructure.
Biodiesel processing involves the production of alkyl esters of long chain fatty acids by reacting the source acid with a low molecular weight alcohol, such as methanol or ethanol. A traditional process for manufacturing fatty acid alkyl esters involves the transesterification of triglycerides using methanol, in the presence of an alkali catalyst. In addition to the desired fatty acid alkyl esters, this process produces an effluent stream comprising glycerol (glycerol), excess alcohol, water, alkyl esters and a mixture of mono, di and triglycerides resulting from the transesterification step. The rapid worldwide expansion of the production of biodiesel fuel since 2000 is creating a rapidly growing supply of byproduct crude glycerol. Over the past year or so the value of crude glycerol has decreased and it is anticipated that biodiesel producers may receive little or no value for this material. A biodiesel plant producing approximately 30,000,000 gallons per year of product generates approximately 22 million pounds of crude glycerol and requires approximately 26 million pounds of methanol (460,000 gallons).
At one time there was a valuable market for glycerol, which assisted the economics of the biodiesel process as a whole. However, with the increase in global biodiesel production, the market price for crude glycerol has crashed. Thus, there is a need in the art for processes capable of converting crude glycerol to more valuable products as well as for reducing the amount of methanol purchased by biodiesel producers from third party sources.